Coronavirus research updates: Vaccine candidate protects monkeys from infection
Nature wades through the literature on the new coronavirus — and summarizes
key papers as they appear.
An experimental coronavirus vaccine seems to have completely prevented infection in most
monkeys that received the jab. Hanneke Schuitemaker at Janssen Vaccines and Prevention in Leiden, the Netherlands, Dan Barouch at Beth Israel Deaconess Medical Center in Boston, Massachusetts, and their
colleagues gave 32 rhesus macaques (Macaca mulatta) a single dose of one of 7 vaccines (N.
B. Mercado et al. Nature http://doi.org/d5d4; 2020). Each vaccine comprised a weakened
respiratory virus coding for one of seven forms of SARS-CoV-2’s spike protein.
After vaccination, nearly all the monkeys made neutralizing antibodies — powerful immune molecules that can block infection — and T cells that trigger other immune responses. When monkeys were exposed to SARS-CoV-2, the most potent of the vaccines prevented lung infection in six out of six animals that received it, and nasal infection in five out of six. Across all the vaccinated monkeys, levels of neutralizing antibodies were associated with protection from SARS-CoV-2 infection, but levels of T cells were not.
Immune cells against the virus are found in unexposed people
Immune cells called T cells are prepared to attack the new coronavirus not only in people with COVID-19, but also in some who have not been exposed to the virus. At first, researchers studying the immune response to SARS-CoV-2 focused mostly on the immune molecules called antibodies, but T cells offer another possible route to immunity.
Andreas Thiel at Charité University Hospital Berlin and his colleagues surveyed blood samples for T cells that react to the SARS-CoV-2 spike protein ( J. Braun et al. Nature http://doi.org/d5bv; 2020).
Viral levels could help to target treatment
The amount of viral RNA in the nose and throat of a person infected with the new coronavirus could help clinicians to decide how best to treat them, according to an analysis of thousands of swabs taken at a hospital in Switzerland.
Onya Opota and his colleagues at Lausanne University Hospital analysed the viral load — the amount of virus in a standard volume of material — of samples taken from 4,172 people infected with SARS-CoV-2 between 1 February and 27 April (D. Jacot et al. Preprint at medRxiv http://doi.org/d4b8; 2020). They noticed two distinct stages of COVID-19. Early in the disease, people have high viral loads, which tend to decline gradually as the disease progresses. This later stage is typically characterized by inflammation. The decline of viral loads could thus
serve as a cue to start treating infected people with anti-inflammatory drugs. But the researchers found no correlation between viral load and the severity of disease, suggesting that it is not a good predictor of a patient’s outcome. The research has not yet been peer reviewed.
Positive trial results raise hopes for a top vaccine candidate
A leading COVID-19 vaccine candidate generates an immune response against the virus and causes few side effects, according to preliminary data from a phase I safety study with 45 participants.
The vaccine is being co-developed by Moderna in Cambridge, Massachusetts, and the US National Institute of Allergy and Infectious Diseases. It consists of RNA instructions that prompt human cells to make the virus’s spike protein, generating an immune response.
Lisa Jackson at Kaiser Permanente Washington Health Research Institute in Seattle and her colleagues gave participants two injections, administered four weeks apart, of one of three different doses of the vaccine (L. A. Jackson et al. N. Engl. J. Med. http://doi.org/d3tt; 2020). Most side effects were mild, although three participants who got the highest dose experienced worse complications, such as a high fever. After the injections, all participants produced immune proteins called antibodies capable of recognizing the SARS-CoV-2 virus, as well as ‘neutralizing antibodies’ that can block infection. A 30,000-participant phase III trial to test whether the vaccine can prevent COVID-19 is set to begin in late July.